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Globular clusters orbit around the center of a galaxy, (Our Milky Way Galaxy has about 150 of them.) and in this image the inhabitants of a planet in one cluster have the pleasure of seeing their parent galaxy rise in all it’s glory every night. As they watch the galaxy rise, there’s more than one set of eyes in the galaxy admiring the globular cluster rising in their night sky.

Bridge to a Galaxy Far

A follow-up to “Bridge to a Galaxy Far”: Morning comes with the rising of the parent gas giant and sister moon as the nearby galaxy that dominated the night sky sets.

Voyager: One who takes a long and sometimes dangerous journey involving travel by sea…or in space.

Forty years ago two intrepid spacecraft, aptly named Voyager 1 and 2, set off on a remarkable journey dubbed the “Grand Tour” to visit the gas giants in the outer solar system. Launching Voyager 2 on August 2 and Voyager 1 on September 5, 1977, NASA took advantage of an alignment of the outer planets that made it possible (economically and energy-wise) to visit at least Jupiter and Saturn and potentially Uranus and Neptune. This alignment wouldn’t occur again for 176 years.

Voyager (Image courtesy of NASA)

Although Voyager 1 launched after Voyager 2 it took a faster path and arrived at Jupiter ahead of Voyager 2. Voyager 1 flew by Jupiter and used the gas giant’s gravity to boost its speed and change direction to head off toward Saturn, retracing Pioneer 11’s journey to Jupiter and Saturn earlier in the decade. The trajectory Voyager 1 had as it approached the ringed giant dictated that it was destined to head out of the solar system above (or north of) the ecliptic, the imaginary plane in which the planets orbit the sun.

NASA had to make a decision with regard to Voyager 2: If Voyager 1 did not successfully complete its pass by Saturn, gathering data on the planet’s largest moon, Titan, Voyager 2’s trajectory would be adjusted to make up for its twin’s shortcomings, otherwise it would encounter the ringed planet and slingshot out to Uranus. To all our benefit, Voyager 1 completed its mission and Voyager 2 went on to visit the ice giants, Uranus and Neptune.

Uranus as seen by Voyager 2. (Image courtesy of NASA/JPL)

Neptune as seen by Voyager 2 (Image courtesy of NASA/JPL)

The probe was not designed from the start to encounter the last two distant planets, but it was designed to be reprogrammed on the fly. So NASA engineers rewrote Voyager 2’s programming to account for the much lower light levels at these greater distances from the sun, allowing the probe to capture the first closeup images of Uranus and Neptune. In 1989, after its encounter with Neptune, Voyager 2 took a southerly path below the ecliptic plane and off toward interstellar space.

Today, both probes are still transmitting data from a half dozen or so instruments, their optical cameras and infrared sensors have long since been shut down to conserve power. Notably, Voyager 1 has passed the boundary between the sun’s influence in our solar system and interstellar space known as the heliopause. We find Voyager 1, the most distant object man has ever sent into space, moving beyond 21 billion kilometers (12.9 billion miles) moving at a speed of 61,000 kph (38,000 mph). It takes almost 19.5 hours for a data transmission to reach Earth from Voyager 1 moving at the speed of light. Voyager 2 is a bit closer at 17 billion kilometers (10.5 billion miles) and is moving slower at about 56,500 kph (35,000 mph) with a transmission time of almost 16 hours.

The radio that the probes carry only transmits at 23 watts. That’s about 5 times a typical cell phone’s transmission power we carry around with us. Since the strength of the signal is reduced by the square of the transmission distance, the signal that we receive from Voyager 1 is really, really small: a tenth of a billionth of a trillionth of a watt. That’s .0000000000000000000001 watts. A very small number! To try to put this is some sort of perspective (and even this is hard to grasp!):

If you dropped a grain of salt from the tabletop to the floor, the energy contained in that grain of salt is 10 x 1 million x 1 billion times larger than the energy contained in Voyager’s signal for one second!

As amazing as it is that these spacecraft have been in space for 40 years and are at these extreme distance, to me, it’s even more amazing that we can detect these signals. We use a network of radio telescopes called the Deep Space Network (DSN) that are superbly designed to pick up these astonishingly small signals. There are three sites across the globe that contain multiple radio telescopes to maintain communication with the distant probes in space. The are located in Canberra Australia, Madrid, Spain and Barstow, California (Goldstone). The facility in Canberra is the only site that has a view of Voyager 2 as it exits the solar system to the south, consequently Canberra had to have its antenna dish increased in diameter in 1987 from 64 meters to 70 meters to be able to track Voyager 2’s diminishing signal.

Radio Telescope, Canberra Au. (Image courtesy of NASA)

The Voyagers will eventually stop transmitting around 2030 as their radioisotope thermoelectric generators (RTGs) finally are depleted. The probes will continue on their respective journeys unimpeded. They will not slow down and will not change direction unless something, or someone interferes with them. They may survive for tens of millions of years – a calling card with a Golden Record carrying representations of the inhabitants from a nondescript little water-planet orbiting a very run-of-the-mill star in an arm of the Milky Way Galaxy.

Hollywood has introduced us to many extraterrestrials, most of them hell-bent on either eating us or conquering and enslaving us. But, what will first contact really be like. What will they look like? What will they smell like? How will they talk and communicate with us? Will this contact be amicable or deadly? So many questions and none of them will be answered until that very first moment we discover that we are not alone in the cosmos. “Contact” depicts our first literal contact with an alien species.

Water, water everywhere. With the prevalence of water all around us (cosmically speaking), it’s not hard to imagine worlds with oceans, lakes, rivers and flowing waterfalls. It would be very interesting to know if the beings populating these planets and moons appreciate water in it’s many dynamical forms as much as we do.

Cassini’s Garden was originally created to commemorate the amazing probe that has been in space for almost 20 years and orbiting Saturn and collecting data since 2004. But, it’s not just the machine, it’s the international group of people that worked together to make the mission happen.

Originally known as Cassini-Huygens, which identifies the Huygens lander that was carried onboard Cassini and successfully touched down on Saturn’s largest moon, Titan, on January 14, 2005. Huygens was provided by the European Space Agency (ESA) and along with the Italian space agency, Agenzia Spaziale Italiana (ASI) and NASA formed the three partners for the mission. In total there were 17 countries involved in the mission. In all, over five thousand people have touched this mission since its development began in 1990; from engineers, technicians, designers, machinists, scientists, astronomers and a host of other specialists from around the world.

The Cassini mission has exemplified the best of what we can do when we cooperate together; something that is painfully lacking around the world today when it is needed most. The data produced by this mission is available to everyone – everybody on this planet benefits from the international cooperation that gave birth to Cassini-Huygens.

Cassini’s Garden shows a monument to the enduring probe that has been erected on Enceladus sometime in the future when we humans are no longer defined by our differences.

The probe has had a few problems during its tour but nothing that has diminished its mission nor prevented it from being extended two more times after its initial 4 year jaunt. The only thing that has forced Cassini to end its mission now is that it is running out of fuel, and to prevent it from potentially contaminating Titan or Enceladus with microbes from Earth, it will be directed to fly into Saturn on September 15, 2017. Truly a sad day for everyone involved with this noble machine or that have followed its mission over the years.

And, speaking of potential for life, a paper has recently been published discussing the data Cassini has collected from a fly-through of the plums of water ice and gas venting from the small moon Enceladus’ southern pole in October of 2015. This data revealed the presence of molecular hydrogen (H2) in the gas/ice cloud, which was mostly water. The presence of hydrogen indicates that there may be hydrothermal vents on the ocean floor of Enceladus. A chemical reaction between the water and the rocks on the ocean floor, driven by the heat could create the hydrogen. This in turn could be used by bacteria as a food source when combined with carbon dioxide dissolved in the water.

The H2 is not direct evidence of life, but compelling evidence that all the right ingredients are there to support life – probably bacterial – like we see around the hydrothermal vents in our oceans. One more feather in Cassini’s cap! Check out NASA’s website for more information on this.

With Cassini setting up to dive between the planet and its inner rings later this month as a finale to its mission, we can expect to see some really amazing images and learn more about this majestic ringed planet than ever before. And, as the data is processed and digested we can expect more revelations about this planet in the years to come.

Thank you to the Cassini team for all their hard work and an amazing ride!